U.S. patent application number 09/859600 was filed with the patent office on 2001-09-20 for brake system for rail cars.
This patent application is currently assigned to Miner Enterprises, Inc.. Invention is credited to Dreese, David F..
Application Number | 20010022467 09/859600 |
Document ID | / |
Family ID | 23353135 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022467 |
Kind Code |
A1 |
Dreese, David F. |
September 20, 2001 |
Brake system for rail cars
Abstract
A brake system for rail cars which contains an air powered fluid
system, a means for providing a separate source of brake force, and
a manifold connected to the air powered fluid system and the means
for providing a separate source of brake force; the manifold
simultaneously delivers pressurized fluid to two movable cylinders
under certain conditions and in response to fluid flow from either
the air powered fluid system or the means for providing a separate
source of brake force; but when both the means for providing a
separate source of brake force and the air powered fluid system are
delivering fluid flow to the manifold, the brake system contains
means for means for terminating the pressure from the separate
source of brake force.
Inventors: |
Dreese, David F.; (Hamburg,
NY) |
Correspondence
Address: |
John W. Harbst
1180 Litchfield Lane
Bartlett
IL
60103
US
|
Assignee: |
Miner Enterprises, Inc.
|
Family ID: |
23353135 |
Appl. No.: |
09/859600 |
Filed: |
May 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09859600 |
May 17, 2001 |
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09345022 |
Jul 2, 1999 |
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6264288 |
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Current U.S.
Class: |
303/15 ;
303/13 |
Current CPC
Class: |
B60T 13/583 20130101;
B61H 1/00 20130101; B61H 13/00 20130101 |
Class at
Publication: |
303/15 ;
303/13 |
International
Class: |
B60T 007/00 |
Claims
I claim:
1. A brake system for rail cars, comprising: (a) an air powered
fluid system with an inlet port and an outlet port for for
producing a first flow of fluid under pressure at said output port
of said air powered fluid system in response to an air flow under
pressure supplied to said inlet port, (b) means for producing a
second flow of fluid under pressure, (c) a manifold connected to
said output port and to said means for producing a second flow of
fluid under pressure, wherein: 1. said manifold contains means for
simultaneously delivering said first flow of fluid under pressure
to each of a first movable cylinder and a second movable cylinder
when said first flow of fluid is at a first specified level of
pressure, 2. said manifold contains means for simultaneously
delivering said second flow of fluid under pressure to each of said
first movable cylinder and said second movable cylinder when said
first flow of fluid is at a pressure lower than a second specified
level of pressure, and 3. said brake system comprises means for
terminating the said second flow of fluid under pressure to said
manifold whenever air flow greater than a third specified level of
pressure is being supplied to said inlet port.
2. The brake system as recited in claim 1, wherein: (a) said brake
system is comprised of a first slack adjuster and a second slack
adjuster attached to said first movable cylinder, (b) said brake
system is comprised of a third slack adjuster and a fourth slack
adjuster attached to said second movable cylinder, and (c) said
first flow of fluid is a first flow of hydraulic fluid.
3. The brake system as recited in claim 2, wherein said second flow
of fluid is a second flow of hydraulic fluid.
4. The brake system as recited in claim 3, wherein said first
movable cylinder is a first hydraulic cylinder.
5. The brake system as recited in claim 4, wherein said second
movable cylinder is a second hydraulic cylinder.
6. The brake system as recited in claim 5, wherein said manifold is
a valve.
7. The brake system as recited in claim 6, wherein said valve is a
spool valve.
8. The brake system as recited in claim 1, wherein said brake
system is attached to a railway truck comprised of a bolster, a
first side frame, a second side frame, a first wheel assembly, and
a second wheel assembly.
9. The brake system as recited in claim 8, wherein said first
hydraulic cylinder is disposed above said bolster.
10. The brake system as recited in claim 9, wherein said second
hydraulic cylinder is disposed above said bolster.
11. The brake system as recited in claim 1, wherein said air
powered fluid system is comprised of means for converting an air
flow under a pressure of from about 50 to about 75 pounds per
square inch which is fed into said inlet port into a fluid flow
with a pressure of from about 500 to about 2,000 pounds per square
inch which is fed out of said outlet port.
12. The brake system as recited in claim 1 1, wherein the ratio of
said pressure of said fluid flow to the pressure of said air flow
is from about 5/1 to about 25/1.
13. The brake system as recited in claim 1, wherein said first
movable cylinder communicates with a first isolation valve
14. The brake system as recited in claim 13, wherein said second
movable cylinder communicates with a second isolation valve.
15. The brake system as recited in claim 1, wherein each of said
first slack adjuster, said second slack adjuster, said third slack
adjuster, and said fourth slack adjuster is comprised of means for
connecting said slack adjuster to a railway truck.
16. The brake system as recited in claim 1, wherein said first
movable cylinder is connected to a first lever arm.
17. The brake system as recited in claim 16, wherein said second
movable cylinder is connected to a second lever arm.
18. The brake system as recited in claim 17, wherein each of said
first and second lever arms is comprised of a substantially
rectangular orifice.
19. An apparatus comprised of a first brake system as recited in
claim 1, and a second brake system as recited in claim 1, and a
third brake system as recited in claim 1, wherein: (a) each of said
first brake system, said second brake system, and said third brake
system is comprised of a separate means for producing a second flow
of fluid under pressure, and (b) each of said separate means for
producing a second flow of fluid is operatively connected to a
single control means for independently controlling and operating
each of said separate means for producing a second flow of
fluid.
20. The apparatus as recited in claim 19, wherein each of said
separate means for produincg a second flow of fluid is a separate
hand pump.
Description
FIELD OF THE INVENTION
[0001] A brake system for rail cars comprising an intensifier, a
spool valve, a pump, and at least two hydraulic or air
cylinders.
BACKGROUND OF THE INVENTION
[0002] The rail network in North America is the largest in the
world, operating with the high axle loads customarily used with
heavy freight hauling railways. For many years there has been a
trend in North America to use heavier and heavier freight cars.
This trend has required designers of brake systems to attempt to
pack more and more brake performance into a smaller and smaller
space.
[0003] In a paper presented at the September, 1971 Annual Meeting
of the Air Brake Association (1971). Thomas H. Engle, Senior
Project Engineer of the New York Air Brake Company (of Starbuck
Avenue, Watertown, N.Y.) disclosed that "About four years ago, our
Company decided that in the long run the best solution for this
squeeze would be a hydro-pneumatic braking system which included
both hand and power braking, and which would use a mechanical lock
on the handbrake so as to hold a car, on which handbrakes had been
applied, even in the absence of hydraulic pressure."
[0004] In 1972, U.S. Pat. No. 3,707,309 was issued to Mr. Engle.
This patent claimed a fluid operated brake system for a railway car
which comprised a hydraulic hand brake control unit which had to be
manually activated and deactivated. Failure to deactivate the
control unit at the appropriate time causes the brakes to maintain
contact with the wheels, thus increasing wear and tear upon the
system and leading to premature failure.
[0005] By no later Mar. 16, 1976, when U.S. Pat. No. 3,944,286
issued to Thomas H. Engle, there existed, according to such patent,
". . . railway regulations which require a crewman to move or
confirm all parking brakes to an `OFF` position . . . ." The patent
disclosed that "The prior art systems . . . may create problems in
use since it is frequently the case that the parking brake has not
been fully unlocked and released by a crewman before an attempt is
made to move the car. Obviously, this can cause numerous delays to
locate the stuck brakes, undue brake wear if some movement does
occur and similar deleterious effects." The solution to this
problem presented in this patent was to provide a brake system
which first required a crewman to release the parking brake of a
particular car. The patentees disclosed that "If, however, the
crewman has failed to even partially release the parking brake of a
particular car, the booster 70 will be ineffective to release
either the brake or the brake locking mechanism."
[0006] Some twenty-three years later on, when Thomas H. Engle's
U.S. Pat. No. 5,746,293 issued in May of 1998, the problems
discussed in his earlier patents had not been solved. Thus, as is
disclosed at lines 50-55 of column 1 of this 1998 Engle patent, ".
. . these hand brakes have been a source of problems. This is
particularly the case when such hand brakes are not released when a
train consist is ready to move over the tracks . . . ."
[0007] About the same time that U.S. Pat. No. 5,746,293 issued to
Mr. Engle, U.S. Pat. No. 5,767,973 issued to Hans J. Naumann. This
latter patent disclosed that ". . . the rail network in the North
America is . . . characterized by an inordinately high number of
railroad accidents and derailments; these incidents occur at a
substantially higher rate in North America than anywhere else in
the world."
[0008] Applicant believes that one of the causes of this problem is
a failure to properly operate and maintain the braking systems on
rail cars. Such lack of proper operation and maintenance is often
due to the complexity of such systems, difficulty of access to the
components in such systems, and the lack of readily apparent visual
indicators warning of system status.
[0009] It is an object of this invention to provide a brake system
which is substantially safer and more reliable than prior art brake
systems.
[0010] It is another object of this invention to provide a brake
system which allows ready visual access to determine whether the
brakes are disengaged.
[0011] It is yet another object of this invention to provide a
brake system which can readily be attached to conventional railway
trucks.
[0012] It is yet another object of this invention to provide a
brake system which can readily be removed from conventional railway
trucks for service.
[0013] It is yet another object of this invention to provide a
brake system which automatically disengages a hand brake upon
application of a train's service brake.
[0014] It is yet another object of this invention to provide a
brake system which is relatively lightweight, small, and
inexpensive.
[0015] It is yet another object of this invention to provide a
brake system which can be used with a railway truck and a railway
car.
[0016] It is yet another object of this invention to provide a
brake system which will require substantially less maintenance than
prior art braking systems, less time to do such maintenance, and
less expense to do such maintenance.
SUMMARY OF THE INVENTION
[0017] In accordance this invention, there is provided a brake
system for rail cars comprised of an intensifier, a spool valve
connected to said intensifier, a pump connected to said spool
valve, a first cylinder connected to said spool valve, and a second
cylinder connected to said spool valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The claimed invention will be described by reference to the
specification and to the following drawings, in which like numerals
refer to like elements, and in which:
[0019] FIG. 1 is a schematic view of one preferred brake apparatus
of the invention mounted on a railway truck,
[0020] FIG. 2 is a schematic view of the brake apparatus of FIG. 1,
showing the position of its components vis-a-vis the railway
truck,
[0021] FIG. 2A is a schematic of a hydraulic circuit involving a
spool valve of the brake apparatus,
[0022] FIG. 3 is a partial side view of the brake apparatus of FIG.
2,
[0023] FIG. 4 is a schematic view of a pin block which may be used
in conjunction with the apparatus of FIG. 1;
[0024] FIG. 5 is a perspective view of a brake lever and clevis
which may be used in conjunction with the pin block of FIG. 4,
and
[0025] FIG. 6 is a perspective view of a brake head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] FIG. 1 is a perspective view of a railway truck 10 onto
which, in the preferred embodiment depicted, a brake system is
mounted. In the embodiment depicted, the brake system is comprised
of hydraulic fluid reservoir 13, air master cylinder 14, fluid
master cylinder 16, spool valve 17, first hydraulic cylinder 18,
second hydraulic cylinder 20, hand pump 22, brake head 24, brake
lever 26, and pin block 28.
[0027] As will be appreciated by those skilled in the art, the hand
pump 22 is but one preferred independent means of providing a
separate source of brake force, commonly used for parking cars when
no air pressure is available at cylinder 14. One may use other
means, manually and/or automatically operated, for applying force
to the brakes. It is preferred, in general, that these other means
include an air or hydraulic cylinder powered by one or more
suitable activation means, which may be manual or automatic.
[0028] In one embodiment, not shown, the hand pump 22 is replaced
with an air or hydraulic cylinder powered by an alternate or
remotely applied force. Thus, by way of illustration, a series of
railroad cars make have a multiplicity of brake systems, each with
a pump 22 centrally operated and controlled from one location.
[0029] In the embodiment depicted in FIG. 1, the brake system is
mounted onto a railway truck 10. As is known to those skilled in
the art, a railway truck supports one end of a rail car and
generally is comprised of bolster 30, side frame 32, side frame 34,
wheel assembly 36, wheel assembly 38, and suspension springs 40.
Railway trucks and their associated braking systems are well known
to those skilled in the art and are described, e.g., in U.S. Pat.
Nos. 5,040,466, 4,981,082, 4,907,514, 4,844,554, 4,838,174,
4,766,818, 4,679,506, 4,669,391, 4,630,715, 4,428,301, and the
like. The disclosure of each of these United States patents is
hereby incorporated by reference into this specification.
[0030] In another embodiment, not shown, the reservoir 13, the
intensifier (comprised of elements 14 and 16), the spool valve 17,
and the pump 22 can be mounted on the associated railway car and
hydraulically connected to the remaining components on the railway
truck 10. In yet another embodiment, the reservoir 13 can be
mounted on bolster 13. As will apparent to those skilled in the
art, it does not matter where these components are located as long
as they are operatively connected to each other.
[0031] FIG. 2 also is a perspective view of railway truck 10 onto
which the components of the preferred brake system 12 are mounted.
Referring to FIG. 2, air from an air reservoir (not shown) is fed
to air master cylinder 14 and hydraulic master cylinder 16, which
collectively act as an intensifier. In general, an air line (not
shown) is connected from one railway car to another; whenever the
pressure in such air line drops below a predetermined value, air is
fed from an air reservoir (not shown) to the line 42 to provide the
desired air pressure to the system.
[0032] Under stable conditions, a constant pressure is applied via
line 42 to elements 14 and 16. When the brakes 44, 46, 48, and 50
are off, the air pressure in line 42 is atmospheric pressure,
generally about 14.7 pounds per square inch. When the brakes 44,
46, 48, and 50 are to be applied, a switch (not shown) is activated
which reduces the pressure in the air line connecting the railway
cars. The reduced pressure state causes the air reservoir (not
shown) to feed air into line 42, thereby increasing the pressure in
such line to a predetermined value, depending upon the size of the
railway truck, often from about 40 to about 70 pounds per square
inch.
[0033] In the preferred embodiment depicted, air master cylinder 14
and hydraulic master cylinder 16 collectively act as an
intensifier, whose function is to convert the increased air
pressure within line 42 to hydraulic pressure; many such
intensifiers comprise only one integral element. These intensifier
units are often referred to as "boosters" or "air powered hydraulic
pumps" or "air powered hydraulic systems" or "air powered hydraulic
intensifiers." They are well known in the art and are described,
e.g., in U.S. Pat. Nos. 5,782,158, 5,772,289, 5,724,852, 5,634,778,
5,375,814, 5,303,643, 5,290,140, 5,271,881, 5,242,358, 4,993,226,
4,784,579, 4,773,222, 4,582,278, 4,011,724, and the like. The
disclosure of each of these United States patents is hereby
incorporated by reference into this specification.
[0034] One such intensifier, which is referred to as a
pneumatic/hydraulic pressure intensifier, is disclosed in U.S. Pat.
No. 5,746,293, the entire disclosure of which is hereby
incorporated by reference into this specification.
[0035] It is preferred that the intensifier, which comprises air
cylinder 14 and hydraulic cylinder 16, be capable of converting
from about 50 to about 75 pounds per square inch of air pressure
into an output hydraulic pressure of from about 500 to about 2,000
pounds per square inch. The ratio of the hydraulic pressure
produced by the intensifier to the input air pressure should
preferably be from about 5/1 to about 25/1 and, in one embodiment,
is from about 8/1 to 17/1.
[0036] For the sake of simplicity of representation, applicant has
depicted the intensifier used in his device as being comprised of
two separate units, air cylinder 14 and hydraulic cylinder 16. As
is well known to those skilled in the art, the commercially
available intensifier units are often sold as one integral package
whose elements provide several different functions. These
commercially available intensifiers, as long as they provide the
degree of pressure amplification required, may be used in the
device of this invention.
[0037] In one embodiment, hydraulic cylinder 16 is an air
cylinder.
[0038] Referring again to FIG. 2, the hydraulic fluid under
amplified pressure is fed via line 52 to spool valve 17. As is
known to those skilled in the art, a spool valve is a slide-type
hydraulic valve in which the movable part is a "spool." These
valves, and their use in brake systems, are well known and are
described, e.g., in U.S. Pat. Nos. 5,882,089, 5,836,845, 5,711,584,
5,624,164, 5,547,264, 5,442,916, 5,417,480, 5,328,002, 5,323,688,
5,188,002, 5,141,293, 5,123,712, and the like. The disclosure of
each of these United States patents is hereby incorporated by
reference into this specification.
[0039] Hydraulic logic circuits for controlling spool valves, and
their outputs, are well known. One such logic circuit is disclosed
in U.S. Pat. No. 4,201,277 of Bruno Meier et al. In this patent,
hydraulic activators are provided with a relief valve which serves
to permit communication between a disengaging cylinder chamber and
a work cylinder chamber. The open position of the relief valve
occurs when the release apparatus for the rotatable friction brake
member is closed. The closed position of the relief valve occurs
after the rotating brake is released. The entire disclosure of this
patent is hereby incorporated by reference into this
specification.
[0040] Other hydraulic logic circuits for controlling spool valves
are disclosed, e.g., in U.S. Pat. Nos. 5,218,997, 4,811,650,
4,812,789, 4,154,261, and the like. The disclosure of each of these
United States patents is hereby incorporated by reference into this
specification. Furthermore, the spool valves can be replaced, in
part or whole, by other hydraulic control valves performing the
same function.
[0041] Referring again to FIG. 2, it will be seen that spool valve
17 is hydraulically conneced to both hydraulic cylinder 16 (via
line 52), and to hand pump 22 (via line 54).
[0042] Spool valve 17 has outputs 56, 58, 60, and 62. For the sake
of simplicity of representation, the circuit logic involving spool
valve 17 is schematically illustrated in FIG. 2A.
[0043] Referring to FIG. 2A, it will be seen that spool valve 17 is
capable of feeding hydraulic fluid via lines 56 and 58 to hydraulic
cylinders 18 and 20, respectively. Such fluid flow will cause these
hydraulic cylinders to move in a manner such that they will
activate the brakes, as will be discussed in more detail later in
this specification.
[0044] The fluid flow through lines 56 and 58 can be caused by
means of fluid from hydraulic cylinder 16, which is caused to flow
because of air pressure in air cylinder 14. As is discussed
elsewhere in this specification, this fluid flow occurs when the
service brake is applied by the engineer; and it flows through both
of lines 56 and 58 to cylinders 18 and 20.
[0045] The activation of hand pump 22 will also cause fluid flow
through lines 56 and 58 and the resultant movement of cylinders 18
and 20.
[0046] When the pressure applied by the hand pump 22 is equal to
the pressure applied through line 52, then the spool within spool
valve 17 will not move, and no fluid will flow to either cylinder
18 or cylinder 20.
[0047] If no service brake is applied by the engineer, then no
fluid will flow through line 52. In that case, fluid flowing though
line 54 because of the use of hand pump 22 will cause the spool to
move within valve 17 and the resultant movement of cylinders 18 and
20.
[0048] If, however, the service brake is applied by the engineer,
the system is designed in such manner that the pressure exerted
through line 52 upon the spool will always be greater than the
pressure exerted upon the spool through line 54. Thus, when the
service brake is applied and the hand brake is not applied, such
pressure will cause the movement of cylinders 18 and 20. When both
the service brake is applied and the hand brake is applied,
cylinders 18 and 20 will still move because of the greater pressure
from line 52. Furthermore, a pressure sensor disposed within line
52 at point 60 will sense the increased the pressure in such line
and cause a pressure controller 62 to open a valve in line 54
located at point 64 and to release pressure back into pump 22.
[0049] The schematic of FIG. 2A provides one means for releasing
the pressure in line 54 when the pressure in line 52 exceeds a
certain specified value. It is only one of many possible means of
achieving this end, all of which are within the scope of this
invention.
[0050] In the preferred embodiment depicted in FIG. 2A, an
isolation valve 66 is disposed within line 58, and an isolation
valve 68 is disposed within line 56.
[0051] When the pressure at point 60 exceeds a certain specified
value, then isolation valves 66 and 68 allow high pressure fluid to
flow back into the system. However, until and unless the pressure
at point 60 exceeds such as specified value, the system will only
allow forward flow in lines 56 and 58 unless and until the pressure
in the cylinders 18 and 20 is manually released back into the
system by means of a release valve (not shown). When such forward
flow has achieved the objective of moving the cylinders 18 and 20
to the desired extent, isolation valves 66 and 68 will close and
not allow flow in either direction until and unless it senses the
pressure in line 52 has exceeded the aforementioned specified
level.
[0052] Referring again to FIG. 2, it will be seen that the
hydraulic cylinders 18 and 20 are disposed above the bolster 30,
thus being removed to some degree from the risk of contact with
moving debris from the wheels of the truck. As will be apparent to
those skilled in the art, the bolster 30 moves up and down on
springs 40. The hydraulic cylinders 18 and 20 are sufficiently
spaced that, even at the maximum height of bolster 30, it will not
contact either of such cylinders. In general, when the truck 10 is
motionless, the hydraulic cylinders 18 and 20 are at least about 2
inches above the bolster 30 when the truck is unloaded.
[0053] Referring again to FIG. 2, attachment pins 70, 72, 74, and
76 are adapted to engage the slack adjusters 78, 80, 82, and 84.
These slack adjusters are shown in greater detail in FIG. 3.
[0054] FIG. 3 is a side view of the side frame 32 (see FIG. 2). It
will be appreciated the side frame on the other side of the truck,
side frame 34, will have a similar configuration.
[0055] Referring to FIG. 3, it will be seen that cylinder 18 is
connected to lever arm 26 at point 86. The structure of lever arm
26 is shown in greater detail in FIG. 5.
[0056] Referring to FIG. 5, a clevis 90, attached to cylinder 18
and equipped with orifices 92 and 94, is aligned with orifice 96 of
lever arm 26 and is removably attached thereto by means of a pin 98
(see FIG. 3). Rectangular orifice 100 of lever arm 26 is adapted to
receive rectangular protrusion 102 of brake head 24 (see FIG. 6).
The rectangular protrusion 102 is comprised of an orifice 104
adapted to be aligned with the orifices 106 and 108 of lever arm 26
(see FIG. 5); and, when so aligned, the lever arm 26 may be
removably attached to the brake head 24 by means of a pin.
[0057] Referring again to FIG. 5, lever arm 26 is also comprised of
an orifice 110 which is adapted to receive rod 112 of pin block
28.
[0058] The connection of lever arm 26 to the hydraulic cylinder 18,
the brake head 24, and the pin block 28 is similar to the
connection of lever arm 27, the free rod end of hydraulic cylinder
18, the brake head 25, and the pin block 29.
[0059] As will be apparent to those skilled in the art, these
connections allow brake heads 24 and 25 to self align to the wheels
37, 39, 41, and 43 (see FIG. 2). This phenomenon allows brake pads
44 and 46 to rotate into positions wherein they are in full contact
with the wheels.
[0060] It will be apparent that many other designs may be used that
will accomplish the same function. Furthermore, spring force or
other means (not shown) can be introduced at the various connection
points to accommodate tolerances and to balance forces or moments
to maintain the shoe 46 in proper relation to the wheel 37.
[0061] Referring again to FIG. 3, it will be seen that slack
adjusters 78 and 80 are connected to hydraulic cylinder 18, one for
limiting movement in one direction, the other for limiting movement
in the other direction. These slack adjusters are well known in the
railway art and are described, e.g., in U.S. Pat. Nos. 5,813,771,
5,615,755, 5,476,269, 5,465,816, 5,253,736, 5,246,081, 5,197,373,
5,067,872, 4,973,206, 4,683,991, 4,676,346, 4,662,485, 4,646,882,
4,530,422, 4,498,711, 4,497,392, 4,457,407, 4,420,066, and the
like. The entire description of each of these United States patents
is hereby incorporated by reference into this specification.
[0062] Furthermore, in the preferred embodiments depicted, the
levers, slack adjusters, and cylinders are supported by and forces
reacted into the side frames. An alternate means culd have these
elements supported by the bolster and/or by another structure.
[0063] It is to be understood that the aforementioned description
is illustrative only and that changes can be made in the apparatus,
in the ingredients and their proportions, and in the sequence of
combinations and process steps, as well as in other aspects of the
invention discussed herein, without departing from the scope of the
invention as defined in the following claims.
[0064] In one embodiment, the air powered fluid system, instead of
producing a hydraulic flow at an increased pressure in response to
an air flow at a lesser pressure, produces a fluid flow at an
increased pressure in response to the an air flow at a lesser
pressure. The term fluid, as used in this specification, is
intended to encompass both air and liquid material.
[0065] The spool valve referred to in this specification acts as a
manifold, directing fluid flow to certain locations in response to
certain conditions. Other manifolds may also be used, and other
valves than spool valves may also be used.
[0066] The hydraulic cylinders referred to in this specification
are but one means of providing linear movement in response to the
flow of fluid under pressure. Other devices, such as other movable
cylinders, also may be used.
* * * * *